Large structures, such as hotels, for example, may need to provide great quantities of hot water on demand to guests. This can be a problem during peak usage hours, e.g., mornings when guests are generally taking warm showers. Many hotels use hot water storage tanks to store hot water so that guests of the hotel may use hot water on demand. Water stored in hot water storage tanks are generally heated using fuel based heaters. Accordingly, energy costs may be high to maintain the hot water temperature. Further, emissions from the heaters may also cause increased pollution and global warming.
Some heat exchange systems have been introduced to enhance efficiency of a fluid heating process. For example, U.S. Pat. No. 4,892,064 to Zappia discloses a unidirectional heat transfer system that includes an enclosed and elongate narrow chamber filled with water. Caps made of a high heat conductive material are positioned on the ends of the chamber. One of the caps is a heater, and includes a thin film lining made of a fibrous material. A wick is connected to the cap and extends the length of the chamber to the opposite cap, which is described as an emitter cap. Heat is transferred from the heat cap, through the wick and into the water. This heat exchange system, however, exposes the water to a foreign element.
A hot water heater and refrigeration assembly is disclosed in U.S. Pat. No. 4,955,207 to Mink. The assembly uses the heat emitted by a refrigeration system to heat water in a hot water heater. More particularly, the assembly includes a heat pipe in the hot water tank to transfer heat provided from the refrigeration system to the hot water tank. This assembly, however, also exposes water in the hot water tank to a foreign element.
U.S. Pat. No. 5,782,104 to Sami et al. discloses an integrated air conditioning system with hot water production. The system includes a hot water tank that feeds a heat exchanger to heat air which is recirculated from a building when required to warm a building. The system also includes a dehumidifier and cooler to dehumidify and cool return air from the building in a recirculation period to cool the building. The system uses a natural gas burner as a source of heat for a hot water tank. Accordingly, the hot water is simply supplied by a gas-fired water heater system. A byproduct of such a system is emissions into the atmosphere.
U.S. Pat. No. 5,901,563 to Yarbrough et al. discloses a heat exchanger for a heat transfer system to be used to cool and dehumidify an interior space. Rejected heat may be transferred to a pool to thereby function as a pool heater. This heat exchanger, however, fails to address possible cross contamination between the refrigerant and the water.
U.S. Pat. No. 7,024,877 to Yap discloses a water heating system including a water storage vessel, a water circuit, first and second heat exchangers, and a vapor compression system. The system discloses the use of carbon dioxide as a refrigerant. Operating carbon dioxide as a refrigerant above the critical point, however, may not, as of yet, be commercially viable. Further, the water heating system does not address prevention of cross contamination between the refrigerant and the water.